The use of apertured films in absorbent articles is well known. As used herein, the term “web” refers to any polymeric web, film or sheet, and the term “apertured web” refers to any web having holes or apertures defined therein. Of particular interest herein are three-dimensional apertured webs in which the apertures are defined by one or more sidewalls in the web which extend from a first or fluid-introduction-facing side of the web and protrude from a second or back-facing side of the web. The wall's protrusion toward the second side gives the web depth, also referred to as “loft.” For purposes of description herein, the web is given an up and down orientation with the first side facing up and the second side facing down. It should be understood, however, that this is for descriptive purposes only and should not be used to limit the embodiments of this invention to a particular spatial orientation.
Apertured webs are particularly useful in absorbent articles since they tend to be preferential in their fluid permeability. That is, the apertures are essentially recesses on the first side but are protrusions on the second side. Since fluid tends to flow down into the recesses more readily than it can flow up and into protrusions, fluid flows preferentially from the first side to the second side. Additionally, the thickness of the web or “loft” created by the aperture walls tends to keep the first side of the web elevated above the absorbent element of the article and, therefore, further prevents the flow of fluid from the second side to the first side.
Having these characteristics, apertured webs are commonly used in absorbent articles such as diapers and feminine pads to promote the flow of fluid away from the user's skin and toward an absorbent core. The apertured web may be used as a top sheet which is adjacent to the user's skin or as an acquisition distribution layer which is disposed between the top sheet and the absorbent core and promotes the even distribution of fluid across the absorbent core. In both cases, the apertured web facilitates distribution of fluids over the absorbent core and prevents “rewetting,” that is, the migration of fluids up from the absorbent core to the user-facing surface of the article. This promotes a drier surface than that of webs which are solely fiber based and have some amount of wicking action.
In addition to minimizing rewetting, apertured webs must have a minimal “strikethrough” time to be effective and avoid undesirable leakage. Strikethrough time, measured in seconds, is the time required for fluid to leave the first side of the apertured web. Strikethrough time is considered a measure of the efficiency of a topsheet in promptly allowing liquid to be absorbed by an absorbent core. Generally, apertured webs are configured to minimize the strikethrough time so that fluid is immediately transmitted to the absorbent core before it has a chance to run off the first side and leak from the article.
Although effective in preventing rewetting, applicants have found that apertured webs in use today could be improved by decreasing strikethrough time, especially for the more viscous exudates, such as menses, since more viscous fluids are less likely to flow down the apertures into the absorbent core beneath. Furthermore, these three-dimensional apertured webs are also not well suited for moving the semi-solid or viscoelastic components in menses, fecal matter, or other fluid substances, from the first side to the second side. Therefore, there is a need for an absorbent article having an apertured layer which not only prevents rewet, but which also facilitates quicker strikethrough, particularly for viscous exudates, and some removal of the viscoelastic components from their surface. The present invention fulfills this need among others.